Fix blocking SSL cert load on event loop (#578)

[danieldotnl]

Summary

• Closes Warning "Detected blocking call" with v9.0.0 #578 — HA blocking-call detector flagged load_verify_locations at scraper setup.
• Pass HA's pre-warmed cached ssl.SSLContext (from homeassistant.util.ssl) into httpx.AsyncClient(verify=...) instead of letting httpx build a fresh context synchronously, which read certifi's CA bundle from disk on the event loop.
• Preserves the v9 per-scraper cookie isolation (still a dedicated httpx.AsyncClient per HttpSession). Going back to get_async_client would have re-broken that.

Why this is a regression in v9.0.0

v8.0.5 used homeassistant.helpers.httpx_client.get_async_client(hass, verify_ssl), which returns HA's shared client built on the cached SSL context — no blocking call ever fired. v9.0.0 commit 8ee795a replaced the shared helper with direct httpx.AsyncClient(verify=bool, ...) to give each scraper its own cookie jar, which reintroduced the cert load on the event loop.

homeassistant.util.ssl pre-warms verifying and no-verify SSL contexts at module-load time precisely so integrations can grab a ready-to-use context without blocking I/O. We use those directly; we don't go through create_async_httpx_client because it wraps aclose with warn_use, which would warn on every HttpSession.async_close().

Test plan

• All 467 existing tests pass (pytest tests/)
• New regression test test_init_does_not_load_verify_locations (parametrized over verify_ssl=True/False) asserts ssl.SSLContext.load_verify_locations is not invoked during HttpSession.__init__
• Manual: load with the reporter's YAML in a HA dev instance and confirm the Detected blocking call to load_verify_locations warning no longer fires at startup or during multiscrape.scrape service calls

🤖 Generated with Claude Code

Summary by CodeRabbit

• Technical Improvements

  • Enhanced SSL certificate verification handling in HTTP sessions for better integration with security infrastructure.

• Tests

  • Added regression tests for HTTP session SSL configuration to ensure reliability.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: c2bc38e4-9084-49e0-aa53-e8a7b761f7dd

📥 Commits

Reviewing files that changed from the base of the PR and between 29edc60 and 927f597.

📒 Files selected for processing (2)

• custom_components/multiscrape/http_session.py
• tests/test_http_session.py

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📝 Walkthrough

Walkthrough

HttpSession now constructs its httpx.AsyncClient with pre-warmed SSL contexts from Home Assistant helpers instead of passing a boolean verify_ssl flag, eliminating a blocking call to load_verify_locations during event loop initialization. A regression test verifies the blocking call no longer occurs.

Changes

SSL Context Pre-warming

Layer / File(s)	Summary
SSL context import and AsyncClient initialization custom_components/multiscrape/http_session.py	Import Home Assistant SSL helpers and update HttpSession to compute ssl_ctx based on verify_ssl (pre-warmed client_context() when True, create_no_verify_ssl_context() when False), then pass the context object to httpx.AsyncClient's verify parameter.
Regression test for blocking call prevention tests/test_http_session.py	Add ssl import and test test_init_does_not_load_verify_locations that parameterizes verify_ssl and verifies ssl.SSLContext.load_verify_locations is not called during HttpSession initialization by patching and asserting the patch was not invoked.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~12 minutes

Poem

🐰 No more blocking calls, the SSL context now glows,
Pre-warmed by Home Assistant's helpers, the event loop flows,
Async can breathe, the warning's gone away,
Clean SSL handshakes for a trouble-free day!

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately describes the main change: fixing a blocking SSL certificate load issue that was occurring on the event loop during HttpSession initialization.
Linked Issues check	✅ Passed	The PR successfully addresses issue #578 by replacing httpx.AsyncClient's default SSL context construction with Home Assistant's pre-warmed context, eliminating the blocking ssl.SSLContext.load_verify_locations call on the event loop.
Out of Scope Changes check	✅ Passed	All changes are directly scoped to resolving the blocking SSL load issue: the http_session.py modification uses HA's pre-warmed context, and the test addition validates the fix.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/578-blocking-ssl-load

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